1. Field of the Invention
The present invention relates to computer networks. More particularly, the present invention relates to a distributed resource reservation system for establishing a path through a multi-dimensional computer network to support isochronous data.
2. Description of the Prior Art
Establishing a path through a network to handle isochronous traffic has in the past been managed by a central routing processor which evaluates the state of the network and reserves resources in a path from a destination to source node. The resources are reserved in a manner that guarantees a delivery time for the isochronous data. However, the central processor may require a significant amount of memory and processing power to evaluate the network and reserve resources to establish paths in an efficient and timely manner. Further, as the network grows, so must the memory and processing capabilities of the central server. Thus, centrally managed schemes do not scale well.
The Resource Reservation Protocol or RSVP protocol is a prior art method for reserving resources to support isochronous traffic in a network wherein the resource reservation facility is distributed throughout the nodes of the network (see the Resource Reservation Protocol or RSVP an overview for which is provided in the text book Managing Bandwidth—Deploying QOS in Enterprise Networks, by Alistair Croll and Eric Packman, Prentice Hall, Upper Saddle River, N.J., 1999; and “Resource Reservation Protocol (RSVP)—Version 1 Functional Specification”, Braden, R., Zhang, L., Berson, S., Herzog, S., Jamin, S., RFC 2205, September 1997, Proposed Standard). The RSVP protocol is illustrated in FIG. 1A which shows a prior art tree network 2 comprising a plurality of nodes wherein a destination node reserves resources in a path toward a source node. In FIG. 1A, node 4A sends a request packet into the network 2 to receive isochronous data from node 4D. As the request packet travels through the network 2, each node in the path (e.g., node 4B and 4C) determines whether it has sufficient resources to service the request and then reserves the resources. FIG. 1B shows a scenario when node 4C cannot service a request from node 4A due to resources having already been reserved to service a request from node 4E. Node 4C sends a reply message to node 4A indicating that the request cannot be serviced. Node 4A must then wait until node 4C has regained sufficient resources to service the request (e.g., when node 4E relinquishes the resources reserved in node 4C). This blocking characteristic of busses and tree networks implementing the RSVP protocol can reduce the aggregate performance of the network, particularly during high traffic periods.
There is, therefore, a need to establish paths for isochronous data in a computer network in a cost effective manner which scales efficiently with the size of the computer network and which avoids the blocking characteristic of the RSVP protocol.